1. Field of the Invention
The present invention relates to a mask for fabricating semiconductor components. The mask contains transparent regions that determine the position of the structures that will be generated on the semiconductor components.
It is generally known that semiconductor components such as single semiconductors and integrated circuits are fabricated using semiconductor wafers. To accomplish this, the various structures that are needed are generated on the semiconductor wafers, for instance by etching and implantation. The size and position of the structures are typically defined in that such semiconductor wafers are covered surface-wide with what is known as photoresist, portions thereof are exposed, and the exposed portions are developed and removed. The exposure occurs with the aid of masks that are transparent in subregions and otherwise opaque (e.g. with the aid of a chromium coating). The correct generation of the desired structures is thus an extremely complex process, which occurs in several steps per structure which must be precisely tuned to one another and in which the utilized materials and aids must also be precisely tuned to one another. The critical parameters are the size and shape (more rectangular or more square) of the generated structures, the configuration of the structures (individual or several adjoining one another), the properties of the photoresist (particularly its reaction to light), the utilized light (intensity, wavelength of the light), the quality of the photoresist, the distance of the mask from the photoresist or the semiconductor wafer (focus), etc. Combinations of values or value ranges of parameters which are suitable for use in a fabrication process are called processing windows.
Because the structures have been progressively miniaturized in recent years, today the diffraction characteristics of the utilized light, the photo characteristics of the resist, and the geometric shape and potential mutual configuration of the structures that are to be generated exert a large influence and are therefore highly important.
It has been shown that a smaller dose of light is needed to correctly expose the photoresist when the structures being generated will be adjacently disposed than when they will not be. Beyond this, it has been shown that, in the latter case, for structures which will have a substantially square surface, the relevant transparent regions of the utilized mask must not also be square, but rather must be rectangular (what are known as “leads” must be taken into consideration). As a result, the long sides of such a rectangle on the mask could be three times as long as the short sides, for example. A substantially higher exposure dose is needed in the latter cases than in the former case. As a result, a plurality of adjacent structures (which are not yet generated) and individual structures (which are not yet generated) that are further removed from these cannot be exposed at the same time in a single exposure process. A different value can also be required for the focus (exposure distance). All of this is connected with the problem of finding the favorable processing window for the respective application instance. This is well known to the person skilled in the art of semiconductor lithography.